Mammalian cells respond to some extracellular stimuli by activating signaling cascades which are mediated by various mitogen-activated protein kinases (MAPKs). Despite the differences in their response to upstream stimuli, the MAP kinase cascades are organized in a similar fashion, consisting of MAP kinase kinase kinases (MAPKKK or MEKK), MAP kinase kinases (MAPKK or MKK) and MAP kinases (MAPK). MAP kinases are a broad family of kinases which includes c-Jun N-Terminal kinases (JNKs), also known as “stress-activated protein kinases” (SAPKs), as well as extracellular signal regulated kinases (ERKs) and p38 MAP kinases. Each of these three MAP kinases sub-families is involved in at least three different but parallel pathways conveying the information triggered by external stimuli. The JNK signaling pathway is activated by exposure of cells to environmental stress—such as chemical toxins, radiation, hypoxia and osmotic shock—as well as by treatment of cells with growth factors or pro-inflammatory cytokines—such as tumour necrosis factor alpha (TNF-α) or interleukin-1 beta (IL-1β).
Two MAP kinase kinases (known as MKKs or MAPKKs), i.e. MKK4 (known also as JNKK1) and MKK7, activate JNK by a dual phosphorylation of specific threonine and tyrosine residues located within a Thr-Pro-Tyr motif on the activation loop on the enzyme, in response to cytokines and stress signals. Even further upstream in the signaling cascade, MKK4 is known to be activated itself also by a MAP kinase kinase kinase, MEKK1 through phosphorylation at serine and threonine residues.
Once activated, JNK binds to the N-terminal region of transcription factor targets and phosphorylates the transcriptional activation domains resulting in the up-regulation of expression of various gene products, which can lead to apoptosis, inflammatory responses or oncogenic processes (1-5).
Some transcription factors known to be JNK substrates are the Jun proteins (c-jun, JunB and JunD), the related transcription factors ATF2 and ATFa, Ets transcription factors such as Elk-1 and Sap-1, the tumor suppressor p53 and a cell death domain protein (DENN).
Three distinct JNK enzymes have been identified as products of the genes JNK1, JNK2 and JNK3 and ten different isoforms of JNK have been identified (3, 6, 7). JNK1 and -2 are ubiquitously expressed in human tissues, whereas JNK3 is selectively expressed in the brain, heart and testes (7, 8, 9, 10). Each isoform binds to the substrates with different affinities, suggesting, in vivo, a substrate specific regulation of the signaling pathways by the different JNK isoforms.
Activation of the JNK pathway has been documented in a number of disease processes, thus providing a rationale for targeting this pathway for drug discovery. In addition, molecular genetic approaches have validated the pathogenic role of this pathway in several diseases.
For example, auto-immune and inflammatory diseases derive from the inappropriate activation of the immune system. Activated immune cells express many genes encoding inflammatory molecules, including cytokines, growth factors, cell surface receptors, cell adhesion molecules and degradative enzymes. Many of these genes are known to be regulated by the JNK pathway, through the activation of the transcription factors c-Jun and ATF-2.
The inhibition of JNK activation in bacterial lipopolysaccharide-stimulated macrophages, effectively modulates the production of the key pro-inflammatory cytokine, TNF-α (11).
The inhibition of JNK activation decreases the transcription factor activation responsible of the inducible expression of matrix metalloproteinases (MMPs) (12), which are known to be responsible of the promotion of cartilage and bone erosion in rheumatoid arthritis and of generalized tissue destruction in other auto-immune diseases.
The JNK cascade is also activated in T cells by antigen stimulation and CD28 receptor co-stimulation (13) and regulates the production of the IL-2 promoter (14). Inappropriate activation of T lymphocytes initiates and perpetuates many auto-immune diseases, including asthma, inflammatory bowel syndrome and multiple sclerosis.
In neurons vulnerable to damage from Alzheimer's disease and in CA1 neurons of patients with acute hypoxia (15), JNK3 protein is highly expressed. The JNK3 gene was also found to be expressed in the damaged regions of the brains of Alzheimer's patients (16). In addition, neurons from JNK3 KO mice were found to become resistant to kainic acid induced neuronal apoptosis compared to neurons from wild-type mice (8).
Based on these findings, the JNK signaling pathway and especially that of JNK2 and JNK3, is thought to be implicated in apoptosis-driven neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, epilepsy and seizures, Huntington's disease, traumatic brain injuries as well as ischemic and hemorrhaging strokes.
Cardiovascular diseases, such as atherosclerosis and restenosis result from defective regulation of growth of the blood vessel wall. The JNK pathway is activated by atherogenic stimuli and regulates local cytokine and growth factor production in vascular cells (17, 18) inducing pro-atherosclerotic gene (19).
Ischemia alone or coupled with reperfusion in the heart, liver, kidney or brain results in cell death and scar formation, which can ultimately lead to congestive heart failure, hepatic disorders, renal failure or cerebral dysfunction. The JNK pathway is activated by ischemia and reperfusion in the heart (20), leading to the activation of JNK-responsive genes and leukcocyte-mediated tissue damage. JNK activation is also observed in kidney (21) or liver (22) following ischemia and reperfusion. The down-regulation of JNKs has been proven to improve renal function and longterm outcome during nephritic and ischemic renal failure (23).
Cancer is characterized by uncontrolled growth, proliferation and migration of cells. In early lung cancer, expression of c-jun is altered and may mediate growth factor signaling in non-small cell lung cancer (24). In addition to regulating c-jun production and activity, JNK activation can regulate phosphorylation of p53, and thus can modulate cell cycle progression (25). Moreover, the role of JNK activation in HTLV-1 (human T cell leukemia virus type 1) mediated tumorgenesis (26) suggests the potential use of JNK inhibitors in cancer treatment (27). Selective inhibition of JNK activation by a naturally occurring JNK inhibitory protein, called JNK-interacting-protein-1 (JIP1), blocks cellular transformation (28). Thus, JNK inhibitors may block transformation and tumor cell growth.
Several small molecules have been proposed as modulators of JNK pathway.
Aryl-oxindole derivatives of respectively the generic formula (A) (WO 00/35909; WO 00/35906; WO 00/35921) and formula (13) (WO 00/64872) have been developed for the treatment of neurodegenerative diseases, inflammation and solid tumors for formula (A) and for the treatment of a broad range of disorders including, neurodegenerative diseases, inflammatory and autoimmune diseases, cardiovascular and bone disorders for formula (B).

Pyrazoloanthrones derivatives of formula (C) have been reported to inhibit JNK for the treatment of neurological degenerative diseases, inflammatory and auto-immune disorders as well as cardiovascular pathologies (WO 01/12609).

Tetrahydro-pyrimidine derivatives of formula (D) were reported to be JNK inhibitors useful in the treatment of a wide range of diseases including neurodegenerative diseases, inflammatory and auto-immune disorders, cardiac and destructive bone pathologies (WO 00/75118).

Other heterocyclic compounds of formula (E) have been proposed to inhibit protein kinases and especially c-Jun-N-Terminal kinases (WO 01/12621) for treating “JNK-mediated conditions” including neurodegenerative diseases, inflammatory and auto-immune disorders, destructive bone disorders, cardiovascular and infectious diseases.

Benzazoles derivatives such as represented by formula (F) (WO 01/47920) have been described as modulators of the JNK pathway and especially as selective inhibitors of JNK2 and/or JNK3 for the treatment of neuronal disorders, auto-immune diseases, cancers and cardiovascular diseases.

Several sulphonamide derivatives of formula (G) (WO 01/23378), sulfonyl amino acid derivatives of formula (H) (WO 01/23379) and sulfonyl hydrazide derivatives of formula (J) (WO 01/23382), were also developed to inhibit JNKs especially JNK2 and JNK3 for treating neurodegenerative diseases, auto-immune disorders, cancers and cardiovascular diseases.

The high relevance of the JNK pathway in some widely spread diseases stresses the need to develop inhibitors, preferentially selective, of JNKs, including JNK3 inhibitors.